This invention relates to vehicle panel assemblies and, more particularly, to vehicle panel assemblies which are mounted to a vehicle with an adhesive.
Conventional window assemblies are mounted to the vehicle body by an adhesive and often in combination with one or more fasteners which are mounted on the window panel or are embedded in a gasket which has been previously extruded or molded on to the window panel. The adhesive often provides the primary attachment to the vehicle and is applied to the surface of the panel, for example by extrusion, after priming of the substrate surface (typically a glass substrate) and/or the vehicle body (typically metal or a composite material). The window assembly is then pressed against the mounting flange or decking of the vehicle body to which the adhesive adheres after curing. Heretofore, these adhesives have been moisture cured, for example the moisture cure BETASEAL(trademark) brand adhesive available from Essex Specialty Products of Auburn Hills, Mich. These moisture cure urethane adhesives, however, are currently applied at the vehicle assembly line and require either robotic application or hand application. Furthermore, the moisture cure adhesives require relatively long cure timesxe2x80x94these adhesives typically take on the order of 120 minutes to cure sufficiently to develop the required xe2x80x9cdeckingxe2x80x9d strength to hold the window assembly in place. Consequently, the window assemblies installed in this manner may require temporary support while moving along the assembly line. Furthermore, the full strength of the adhesive requires a cure of about 24 to 72 hours, depending on environmental conditions. In addition, these cure periods are sensitive to the surrounding environment. Where the manufacturing plant is located in an area having low humidity, the cure time is significantly longer than in an area having high humidity. Consequently, standardizing such installations is difficult.
In addition to the relatively long cure time, the chemicals forming the adhesive and the adhesive primers require special handling. The adhesive must be contained in a very low moisture or moisture-free environment before application onto the glass panel to avoid premature curing. Furthermore, the adhesive and primer chemicals require special clean-up procedures and inventorying to assure full effectiveness of the adhesive. Moreover, these chemicals require proper ventilation, and the personnel handling the chemicals require protective gear. Consequently, in-vehicle-plant applications are labor intensive, increase assembly line-time, potentially increase the frequency of down-time when the adhesive is improperly applied, for example when the adhesive is dripped on other areas of the vehicle, and are, therefore, costly.
More recently, proposals have been made to control the curing process of the adhesive by covering the adhesive with a barrier film which is then subsequently peeled off the bead at the assembly line to allow installation and curing. One such example is disclosed in U.S. Pat. No. 4,933,032 to Kunert. Kunert ""032 also proposes the use of heat or irradiation to actuate a multi-component polyurethane adhesive, which contains an initiating or reaction component in inactivated form, for example in the form of micro-capsules, which are activated by the heat or irradiation before assembly of the glazing. While the removable barrier films and multi-component polyurethane adhesive theoretically remove the adhesive application process from the assembly line, numerous problems still remain. The extrusion and film application process is complicated, and the film can be vulnerable to tearing or damage during transportation. Furthermore, these films still require removal and disposal. Moreover, the barrier film must be accurately placed, otherwise, the exposed portions of the adhesive are prematurely cured and may be ineffective as a bonding agent.
The recent trend in vehicles is to produce a stream line or aerodynamic vehicle with larger windows to improve visibility. As a result the window assemblies often require compound curvatures. These compound curvatures make it hard to heat the panel uniformly. Furthermore, newer window panels include laminated substrates, moldings, and attachments which tend to degrade when subject to high temperatures. In order to heat such micro-capsule-containing adhesives over a period of time consistent with in-line processing, relatively high energy is required. In addition to possible degradation of the panel substrate, of the moldings, and of the attachments, the bead of adhesive is also subject to degradation if overheated. Perhaps for these and other reasons, heretofore, no xe2x80x9cready-to-installxe2x80x9d window or panel assemblies have been successfully made or commercialized.
Consequently, there is a need for a xe2x80x9cready to installxe2x80x9d panel assembly, for example a modular window, which can be quickly installed or xe2x80x9cdeckedxe2x80x9d in a vehicle or the like in an assembly line. Preferably, the modular window can be preassembled with an adhesive already applied at a location remote from a vehicle assembly plant to eliminate additional manufacturing time at the assembly line, handling of extra materials, on-line purging, which is required to eliminate unused portions of the moisture cured urethane in the dispenser nozzle, handling of chemistry in the vehicle manufacturing plant, including the adhesives and adhesive primers, and humidity control equipment and yet can be xe2x80x9cdeckedxe2x80x9d with the adhesive which is not activated until just prior to installation and which develops sufficient decking strength to hold the modular window in place.
Accordingly, the present invention provides a method of preparing a vehicle panel assembly for attaching the panel assembly to a vehicle. The vehicle panel assembly includes a substrate and a bead of ready-to-install heat activated adhesive. The substrate includes first and second sides. The bead of heat activated adhesive is applied to the second side of the panel. The panel is prepared by heating the first side of the substrate and by heating the outer skin portion of the bead such that the core portion of the bead reaches its activation temperature. In addition, after heating, the panel assembly is cooled to permit manual handling of the panel assembly.
In preferred forms, the panel assembly is cooled by directing air onto a portion of the substrate to cool the substrate to permit handling of the vehicle panel assembly. For example, the panel assembly may be cooled by blowing a gaseous stream onto the peripheral portion of the substrate preferably at an angle in a range of approximately 5xc2x0 to 90xc2x0. For example, the gaseous stream may include air or an inert gas, such as argon or nitrogen or the like. In further forms, the gaseous stream is localized on the peripheral portion of the substrate to cool the substrate, for example by blowing the gaseous stream on the peripheral portion with a knife edge blower.
In other forms, the method of preparing the vehicle panel assembly further includes balancing the heating and the cooling to ensure that the central core portion of the bead at least reaches its heat activation temperature while cooling the substrate below 250xc2x0 F. More preferably, the heating and cooling is balanced to ensure that the central core portion of the bead at least reaches its heat activation temperature while cooling the substrate below 175xc2x0 F. Most preferably, the heating and cooling is balanced such that the central core portion of the bead at least reaches its heat activation temperature while cooling the substrate below 120xc2x0 F. Preferably, the substrate is cooled to a desired temperature within fifteen minutes or less after heating, more preferably within about nine minutes or less after heating, and most preferably less than two minutes after heating. In addition, the method preferably includes balancing the heat on the first side and the heat on the second side to heat the central core portion to at least a heat activation temperature in a range of about 50xc2x0 C. to 160xc2x0 C. while maintaining an outer skin surface temperature at least no more than about 40xc2x0 C. greater than the central core portion temperature and cooling substrate temperature below 120xc2x0 F. within a period of about fifteen minutes or less after heating.
In preferred forms, the heating of the outer skin portion includes heating with longwave infrared radiation, for example with longwave infrared radiation with a thermal mass temperature in a range of about 450xc2x0 F. to about 900xc2x0 F. The first side of the substrate is preferably heated with shortwave infrared radiation.
In other forms, the cooling is initiated after the adhesive has reached a heat activation temperature.
According to another aspect of the invention, the vehicle panel includes a substrate and a bead of heat activated adhesive. The substrate has first and second sides and a peripheral portion, with the peripheral portion including a gasket which extends over at least a portion of the second side of the substrate. The bead of ready-to-install heat activated adhesive is applied to the gasket. In this aspect, the method of preparing the panel assembly includes heating the first side of the substrate adjacent gasket whereby the substrate heats the gasket to heat the interface portion of the bead and heating outer skin portion of the bead to thereby heat the central core portion of the bead and activate the ready-to-install heat activated adhesive.
In further aspects, the method includes cooling the substrate after heating the first side of the substrate and the outer skin portion of the bead. In one form, the substrate is cooled after the ready-to-install heat activated adhesive is activated.
According to yet another form of the invention, a method for preparing a vehicle panel assembly for attaching to a vehicle includes heating the vehicle panel substrate with a shortwave radiation source thereby heating the bead with a substrate through the bead""s interface portion and heating the bead with a source of longwave infrared radiation whereby the core of the bead at least reaches an activation temperature. The method further includes cooling the substrate after heating the bead thereby permitting handling of the vehicle panel assembly after the bead of adhesive is activated.
In further forms, the cooling may be initiated after the core of the bead has reached its activation temperature, with the substrate being cooled to a desired temperature within 15 minutes or less after cooling is initiated, more preferably with the substrate being cooled within 9 minutes or less after cooling is initiated, and most preferably with the substrate being cooled within 2 minutes or less after cooling is initiated.
In other forms, the substrate is heated by positioning at least one heating shortwave infrared emitting lamp spaced from the first side of the substrate and aligning the lamp with the central axis. However, the lamps may be offset from the central axis less than twenty-four inches, more preferably less than twelve inches and most preferably less than one inch from central axis. The lamp is preferably spaced less than twenty-four inches from the first side of the substrate, more preferably, less than twelve inches, and most preferably less than three inches from the first side of the substrate.
In further forms, the bead is heated by positioning the source of longwave radiation spaced from the second side of the substrate, for example, preferably less than twenty-four inches from the second side of the substrate, more preferably less than twelve inches from the second side of the substrate and most preferably less than three inches from the second side of the substrate. Further, the source of longwave radiation is preferably aligned with the central axis of the bead. However, similar to the shortwave radiation source, the longwave radiation source can be offset from the central axis less than twenty-four inches, more preferably less than twelve inches, and most preferably less than one inch from the central axis.
The improved method disclosed herein provides a xe2x80x9cready-to-installxe2x80x9d panel assembly, which is particularly suitable for window assemblies. The panel assembly is pre-assembled with a bead of heat activated adhesive extruded or otherwise applied on a second side of the panel substrate. The bead of adhesive is activated by the application of longwave and shortwave infrared radiation which are respectively applied to the bead of adhesive and to an opposed side of the panel substrate, which indirectly heats the bead. The panel substrate and other components, such as molded gaskets and the like, are protected from the shortwave infrared radiation by localizing the shortwave infrared radiation on a discrete portion of the first side of the substrate panel which is aligned with the bead of adhesive. In this manner, the bead of adhesive is quickly and uniformly heated without the associated degradation which often occurs with high energy heating. Further, the panel assembly is cooled to permit manual handling of the panel assembly soon after the assembly has been heated and the adhesive has been activated.
These and other objects, advantages, and purposes and features of the invention will become more apparent form a study of the drawings, specification, and claims which follow.